maillemaker wrote:
If its purpose is to isolate the house batteries from the starting batteries during cranking and when the engine is OFF, it will only be ON when the engine is running and you are trying to charge the house batteries from the engine. I am certain that your engine alternator can not generate anything near 300A !
In my RV, there is a momentary switch option to gang the house batteries to the engine batteries during cranking, so that the house batteries provide an emergency jump start if the engine battery is dead.
I think engine starters can pull 200-500A if I'm googling correctly.
Most all RV's have what's called an "Auxiliary Start Switch". Energizes the isolator solenoid thus connecting both banks so you can start the rig. It can EASILY pull 200+ amps and can easily blow the house battery fuse! I have done it myself once.
I was at a state beach, a new Discovery pulled in and the owner was walking around scratching his head. I asked him what the issue was. He told me he had no interior lights, every 12v item was dead.
First thing I looked at was his house battery fuse and sure enough, it was blown. He had a low chassis battery and tried to use the Aux Start Switch.
If I ever run into a dead or low chassis battery I'm going to hold that Aux Start Switch for about 3 to 5 minutes to get some juice into the coach batteries B$ trying to crank her over.
